The worsening energy shortage has increased the need to decrease the amount of energy which is wasted. Much energy can be conserved by limiting the air conditioning and heating of unoccupied rooms in hotels, motels, and other buildings. The saving can be maximized if room air conditioners and heaters are turned on shortly before a room is occupied and are turned off promptly after a room is vacated. This is best accomplished from a centralized control point in a building where information on the status of each room is maintained, such as at the front desk of a hotel or motel. Energy conservation can be accomplished with relatively little additional expense if the building is already provided with a computer-controlled system for recording and displaying the status of each room, and the charges accumulated by the occupants of the respective rooms.